A wheel with 8 metallic spokes each 50 cm long is rotated with a speed of 120 rev/min in a plane normal to the horizontal component of the earth's magnetic field. The earth's magnetic field at the place is 0.4 G and the angle of dip is 60°. The induced emf between the axle and the rim of the wheel is:

$2×10^{-6} V$ $1.23 × 10^{-3} V$ $3.14×10^{-5} V$ $6×10^{-8} V$

$3.14×10^{-5} V$

The correct answer is Option (3) → $3.14×10^{-5} V$